The impact of antisite disorder on the physical properties of La<inf>2</inf>FeB"O<inf>6</inf> (Bʺ = Fe, Ni and Co) double perovskites

Abstract

The synthesis, structural, morphological characterization, as well as the magnetic properties, of a double perovskite family La2FeB"O6, (Bʺ = Fe, Co, and Ni) were studied. The investigated samples were synthesized by a modified citrate auto combustion route. The crystal structure and microstructure were refined applying Rietveld profile refinements with the help of the Maud Program. The difference between the detected and simulated powder diffraction patterns is minimized using the reliability index parameter. The presence of nanometric crystallite was confirmed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The presence of multiple oxidation states of Fe, Co and Ni were confirmed by X-ray photoelectron spectroscopy (XPS). The maximum value of exchange bias was obtained for La2Fe2O6, while La2FeNiO6 recorded the minimum value. In the investigated samples, the different natures of antiphase boundaries (APBs) cause the lack of magnetic saturation at relatively high magnetic fields. On the other side, the existence of various magnetic interactions with different magnetic antisite disorder (ASD) initiate the system to change to spin glass state.